a) 5½ – 14³/⁷ ÷ ⁹/¹³ – 3⁴/⁷ ÷ ⁹/¹³ b) ³⁸/⁴⁵ – (⁸/⁴⁵ – ¹⁷/⁵¹ – ³/¹¹ ) c) 2½ + 19³/¹¹ × ⁷/²⁶- 6³/¹¹ × ⁷/²⁶

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1. Đáp án:

    $a)\dfrac{-41}{2}\\
   b)
   \dfrac{14}{11}\\
   c)6$

   Giải thích các bước giải:

    $a)5\dfrac{1}{2}-14\dfrac{3}{7}:\dfrac{9}{13}-3\dfrac{4}{7}:\dfrac{9}{13}\\
   =\dfrac{11}{2}-14\dfrac{3}{7}.\dfrac{13}{9}-3\dfrac{4}{7}.\dfrac{13}{9}\\
   =\dfrac{11}{2}-\dfrac{13}{9}\left (14\dfrac{3}{7}+3\dfrac{4}{7} \right )\\
   =\dfrac{11}{2}-\dfrac{13}{9}.18\\
   =\dfrac{11}{2}-13.2\\
   =\dfrac{11}{2}-\dfrac{26.2}{2}\\
   =\dfrac{-41}{2}\\
   b)
   \dfrac{38}{45}-\left ( \dfrac{8}{45}-\dfrac{17}{51}-\dfrac{3}{11} \right )\\
   =\dfrac{38}{45}-\dfrac{8}{45}+\dfrac{17}{51}+\dfrac{3}{11}\\
   =\dfrac{30}{45}+\dfrac{17:17}{51:17}+\dfrac{3}{11}\\
   =\dfrac{2}{3}+\dfrac{1}{3}+\dfrac{3}{11}\\
   =\dfrac{2+1}{3}+\dfrac{3}{11}\\
   =1+\dfrac{3}{11}\\
   =\dfrac{11}{11}+\dfrac{3}{11}\\
   =\dfrac{14}{11}\\
   c)2\dfrac{1}{2}+19\dfrac{3}{11}.\dfrac{7}{26}-6\dfrac{3}{11}.\dfrac{7}{26}\\
   =2\dfrac{1}{2}+\dfrac{7}{26}\left (19\dfrac{3}{11}-6\dfrac{3}{11} \right )\\
   =\dfrac{5}{2}+\dfrac{7}{26}.13\\
   =\dfrac{5}{2}+\dfrac{7}{2}\\
   =\dfrac{12}{2}\\
   =6$

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